The twin-belt casting method is a continuous casting method pouring a melt between two water cooled rotating belts facing each other in the vertical direction, cooling it from the outside surfaces of the belts to solidify the melt to form a slab, continuously pulling out the slab from the side of the assembly of the belts opposite to where the melt was poured, and taking it up in a coil.
In particular, in an aluminum alloy slab continuous casting and rolling line having a twin-belt casting machine and skin pass rolling machine, to obtain a sound aluminum alloy continuously cast and rolled slab, the belt speed of the twin-belt casting machine and the roll speed of the skin pass rolling machine have to be suitably controlled.
The structure of a casting machine for continuously casting an aluminum melt is described in the cooling guide system of a belt in continuous belt casting of a metal strip (Japanese National Publication (A) No. 2004-505774) and control of the heat flow of metal continuous casting (Japanese National Publication (A) No. 2004-508203). Japanese National Publication (A) No, 2004-505774 relates to a system and method for cooling and guiding a casting belt of a twin-belt casting machine, while Japanese National Publication (A) No. 2004-508203 relates to a method of casting a molten metal for producing an ingot for a casting metal strip while controlling the speed to eliminate heat to avoid surface defects and warping of the casting cavity. Neither Japanese National Publication (A) No. 2004-505774 nor Japanese National Publication (A) No. 2004-508203 has any description of speed control of a twin-belt casting machine and thin slab speed control at the outlet side.
On the other hand, regarding the speed of a continuous casting machine of a ferrous metal, for example Japanese Patent Publication (A) No. 54-39321 discloses a continuous casting method pouring molten steel from above a mold formed by a casting wheel rotating in a certain direction and a belt moving along part of its outer circumference in the same direction as the casting wheel and pulling out a cast strip from the bottom of the mold, the belt caster type continuous casting method for steel characterized by reducing the cast strip pullout speed to a speed of an extent where the melt surface at the rear end of the cast strip is solidified and no molten metal leaks from the rear end of the cast strip when the rear end of the cast strip reaches the inside of the mold. Further, Japanese Patent Publication (A) No. 59-24563 discloses a method of operating a continuous casting system comprising adjusting a pullout speed of a cast strip so that a speed of movement of the cast strip from a meniscus of molten steel in a mold to 150 mm in a height direction becomes within 2 seconds and thereby suitable for taking up a thin wide cast strip of only the sheet thickness into a coil shape and able to obtain a high quality cast strip with extremely few surface flaws and internal cracks. Japanese Patent Publication (A) No. 54-39321 and Japanese Patent Publication (A) No. 59-24563 disclose a method of control and a method of adjustment of the cast strip pullout speed, but do not disclose a method of control of the belt speed of the twin-belt casting machine and the roll speed of the hot rolling machine in the case of continuous hot rolling of a cast strip.